Don't initialize PostGIS-specific stuff for non-db connections

Refs #16969.

django/contrib/gis/db/backends/postgis/base.py

+from django.db.backends.creation import NO_DB_ALIAS
 from django.db.backends.postgresql_psycopg2.base import DatabaseWrapper as Psycopg2DatabaseWrapper
 from django.contrib.gis.db.backends.postgis.creation import PostGISCreation
 from django.contrib.gis.db.backends.postgis.introspection import PostGISIntrospection
@@ -7,6 +8,7 @@ from django.contrib.gis.db.backends.postgis.operations import PostGISOperations
 class DatabaseWrapper(Psycopg2DatabaseWrapper):
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
-        self.creation = PostGISCreation(self)
-        self.ops = PostGISOperations(self)
-        self.introspection = PostGISIntrospection(self)
+        if kwargs.get('alias', '') != NO_DB_ALIAS:
+            self.creation = PostGISCreation(self)
+            self.ops = PostGISOperations(self)
+            self.introspection = PostGISIntrospection(self)

django/db/backends/creation.py

@@ -14,6 +14,7 @@ from .utils import truncate_name
 # The prefix to put on the default database name when creating
 # the test database.
 TEST_DATABASE_PREFIX = 'test_'
+NO_DB_ALIAS = '__no_db__'
 
 
 class BaseDatabaseCreation(object):
@@ -44,7 +45,7 @@ class BaseDatabaseCreation(object):
         backend = load_backend(settings_dict['ENGINE'])
         nodb_connection = backend.DatabaseWrapper(
              settings_dict,
-             alias='__no_db__',
+             alias=NO_DB_ALIAS,
              allow_thread_sharing=False)
         return nodb_connection